Posterior reversible encephalopathy syndrome (PRES): Should more attention be paid to the atypical forms?

Posterior reversible encephalopathy syndrome (PRES) is an uncommon, but important, pathology affecting primarily the posterior cerebral circulation. Typical imaging features include vasogenic edema involving the bilateral occipital and parietal lobes. We report 4 cases of atypical PRES: The first one is a 59-year-old woman with a medical history of diabetes and hypertension who presented a consciousness disorder. MRI of this patient revealed signal abnormalities in the thalamus, the cerebellum, the brainstem and the corpus callosum with microbleeds and vascularization disorders. The second patient is a 41-year-old woman admitted for right hemiparesis and facial paralysis. Physical examination found a hypertension and the atypical imaging features on MRI were low ADC values with a pearl necklace appearance on ARM sequences. The third patient is a 32-year-old woman who undergone a surgery for an ectopic pregnancy and went in a coma for 8 days. Physical and biological parameters were normal. Diagnosis was delayed because of atypical signal abnormalities in caudal and lentiform nuclei that worsened on follow-up MRI, resulting in a dramatic evolution to bilateral cecity and psychosis. The last case is a 34-year-old woman with terminal renal failure hospitalized for spontaneously resolving tonic-clonic seizures. Biology showed high uremia and brain MRI revealed a gyriform enhancement at gadolinium injection with unilateral putamen lesion. The patient improved after blood purification. Knowledge of these atypical findings can help the radiologist make an accurate, timely diagnosis, and improve patient care.